2l6 



NATURE 



\y2ily II, 1S7: 



cumstances here set forth would, we declare, be a calamity to 

 Knglish science andascaiidal to the Knglish Government. With 

 the power to avert this in your hands, we ap|ieal to your justice 

 to do so. The difficulty of removing tlie directorship of ls.ew 

 from the Department of Works cannot surely be insuperable; 

 or if it be, it nnist be possible to t'fve such a position to the 

 Director, and such definition to his duties, as sliall in future 

 shield him from the exercise of aulhoiily which has been so 

 wantonly abused. 



Charles Lyei.i, 



Charlks Dakwin 



(iEORGE liENi'HAM, I'rcs. Limi. Sociely 



Henry Holland, I'res. Royal Institution 



George Burrows, I'res. Roy. Coll. of Physicians 



George Busk, Pres. Roy. Coll. of Surgeons 



H. C. Kawlinson, Pres. Roy. Geogr. Society 



James Paget 



William Stottiswoode 



T. H. MU.XLEY 



John Tyndall 



PROFESSOR AGASSIZ'S SOUTH AMERICAN 



EXPEDITION 



I. 



pROF. AGASSIZ'S Second Report to Prof. B. Peirce, Super- 

 ^ intendent of the United States Coast Survey, dated U.S. 

 steamer //(7w/tv, Concepcion Bay, June i, is given in the A't-:,' 

 York I'ribuiic of June 26. The Report is of so great value and 

 interest, that we reprint it entire : — 



Since I sent my first report concerning erratics in the Southern 

 Temperate Zone, I have been much engrossed with this subject, 

 and have turned my attention chiefly that way, leaving to Pour- 

 tales the superintendence of the dredging, and to Steindachner 

 and Blake the care of the zoological specimens. 



On the eastern coast of Patagonia I had but little opportunity 

 of adding to the information I had already obtained at Monte 

 Video. It was not till we put into San Malhias Bay for some 

 rep.airs that I could gather a few new facts. This bay is par- 

 ticularly interesting, because one can there compare the position 

 of the teitiary beds in the cliffs bordering the Atlantic with 

 that of similar beds in the cliffs along the northern shore of the 

 bay. The southern exposure of tlie latter runs for nearly a 

 hundred miles at about right angles with the sea coast. In 

 both cases the outcrops of the beds are so nearly parallel with 

 the surface of the sea, that whatever may have been their 

 changes of level with reference to the ocean, they still retain tlie 

 horizontal position in which they were deposited. It is of the 

 utmost importance to remember this point when considering the 

 distribution of the erratics over this part of the country with 

 reference to the agency that may have transported them to their 

 present resting-place. Among these tertiary deposits are well- 

 marked banks of colossal oysters of considerable extent, one of 

 which coincides with the level of low water, whde another 

 stands at least twenty-five feet higher. The difference of level 

 between these two great beds of oysters is so considerable as to 

 suggest a subsistence of the sea bottom during the deposition of 

 tlie tertiary beds. Higher up there are outer layers full of smaller 

 fossils — some about ten, others about twenty feet above the 

 second oyster-bed. The oyster-beds are perfectly parallel with 

 one another, and separated by thin layers of clay and sand. 

 And so, also, are the upper tertiary beds containing the smaller 

 fossils. Among these, one bank consists almost entirely of large 

 numbers of a species of Siutclla with a single perforation in tlie 

 posterior interambulacral area. This bank is particularly well 

 marked. A bank of hard sand higher up is also conspicuous, 

 and so is another of hard clay standing about 100 feet above the 

 sea-line. 



As we shall see hereafter, and as Darwin has already stated, 

 these tertiary beds extend all over eastern Patagonia, including 

 the Straits of Magellan as far as Sandy Point. In consequence 

 of disintegration the harder beds form as many retreating shelves, 

 like stairs, upon the slope of the shore bank. \\'herever surface 

 denudation has taken place these shelves give rise to terraces, 

 stretching horizontally at various heights all over the plains of 

 Patagonia. The scenery at Cliff End reminded me somewhat of 

 Gay Head and its tertiary formation, except that the upper part 

 of the Cliff consisted chiefly of sandy clays, alternating with 

 which arc two distinct horizontal beds of considerable thickness. 



fonned entirely of pebbles, rather small and uniform in size. 

 These pebbles vary from the dimensions of a pea or a hazel nut 

 to that of the fist, or more ; but there are no boulders or large 

 fragments of rock among them. It is noteworthy that, while 

 these pebbles alternate in regular stratification w ith the sandy 

 clays in the upper part of the cliff, they also occur upon the 

 shelves below. In the latter case, however, they form only 

 superficial deposits, and do not penetrate with ihe beds on which 

 they rest into the interior of the strata. It h.as occurred to me 

 tli.at similar superficial accumulations of pebbles upon the 

 shelves bordering the bed of the .Santa Cruz River may have 

 been mistaken by Darwin for indications of successive upheavals. 

 It is certain that there are no beaches here, marking successive 

 steps of the upheaval of the country. What Darwin has con- 

 sidered as evidence of a gradual rise of the shore are ilie denuded 

 surfaces of the horizontal tertiary deposits which everywhere form 

 parallel terraces. .\s formyself, 1 see here no evidence of upheaval 

 except the level of the fossil beds of oysters and other fossils in 

 the tertiary beds above the water, and the presence of fresh 

 shells of living species upon and above the shore banks. These, 

 however, only indicate that an upheaval has taken place since 

 the deposition of the tertiaries, and while the shells now living 

 already existed, without pointing to the rise by successive steps. 

 Still less does it appear to me that the country has been sub- 

 merged during the transposition of the erratics. Toward the 

 west end of San Mathias B.ay, at Port San Antonio, where ex- 

 tensive denudations have taken place in the very formations here 

 described, these same pebbles occur again. But at Port San 

 Antonio, instead of being well defined, continuous horizontal 

 beds above the sea-level, they are shore pebbles, covering in a 

 deep layer the whole extent of the beach, the inequality of which 

 they follow. Their position here shows, beyond the possibility 

 of doubt, tliat the whole set of beds above which they rest in 

 regular stratification at Cliff End has been completely broken 

 down and recently removed by the action of the sea, and the 

 pebbles themselves thus brought to the sea level. Of course it 

 follows that these pebbles have not been ground upon the modern 

 beach, but upon an older foundation, corresponding at the time 

 to the level at which the pebble beds now stand at Cliff End. 



So far the facts. I am inclined to add, as an inference from 

 subsequent observations made farther south, the relation of w hich 

 to the facts above stated seem to me clear, that these pebbles 

 have passed through the mill of a glacier's bottom before they 

 were worked up by the floods into their present position in the 

 beds of Cliff" End and upon the beach of San Antonio ; and I 

 do not see why the floods which formed these denudations could 

 not as well have been the result of the melting of ice at the close 

 of the glacial period, as the result of a change of level between 

 land and sea. As soon as geologists have learned tu appreciate 

 the extent to which our globe has been covered and fashioned by 

 ice, they may be less inclined to advocate changes of level be- 

 tween land and sea, wherever they meet with the evidence of the 

 action of the water, especially wheie no marine remains of any 

 kind mark the presence of the sea. As I have already said, the 

 small and remarkably uniform size of the pebbles in Poit San 

 Antonio is particularly noticeable, and also the fact that none but 

 hard rocks, indeed, only the very hardest kind of rocks, are re- 

 presented among them. 



(To be coiUiiincd.) 



CONTENTS Page 



Economic Entomology jg; 



Origin and Destiny of Man lyS 



Our Book Shelf j,^r> 



Letters to the Editor: — 



The Rigidity of the Earth and the Liquidity of Lavas.— T'ruf. T. 



Stehky Hunt. F.R.S :oa 



FouUag of the Nile. — Rev. Caiion Kingsley, F.L.S :;oo 



Volcanoes of Central France. — Henry Norton --^o 



The Wanderings of the Esquimaux. -Dr. John Rar, F.R.G.S. . 2ot 



Tlie Aurora of February 4.— H. C. Russell 202 



The Zoological Station at Naples 202 



On Ali-ine Maps. Uy Edwahd Why.mper 203 



Evans's Stone Lmplements of Gkkat Britain. I. {IVttk Ulus^ 



trations) 20S 



The Hunterian Museum 2o3 



Notes 209 



Mk. Ayrton and Dr. Hooker :ji[ 



Pkok. AcAisu's South American Expedition. 1 21G 



